What does it mean that even a child is known by his deeds (Proverbs 20:11)?

Authenticity and truthfulness are marks of godly character. God is concerned with who we are on the inside and not the image we portray externally (1 Samuel 16:7). According to Solomon, actions do indeed speak louder than words to reveal the truth about our inner selves:

Proverbs 20:11 is an indictment against hypocrisy and deceit, attitudes that displease God and are condemned in Scripture (Psalm 26:4; Isaiah 29:13; Matthew 23:27–28; Luke 12:1–2; 20:46–47; Titus 1:16; 1 Peter 2:1). A hypocrite pretends to be something or someone on the outside to hide his inner reality. But God knows who we are and what we are truly like on the inside (Luke 16:15). He sees through false displays of purity and righteousness to uncover what lies in our hearts.

Not only does God see below the surface to unmask duplicity, but eventually people will see through it, too. Thus, Solomon warns the wise person to consider the danger of deception and duplicity (Proverbs 6:12–15; 10:10; 11:3; 16:30; 20:14; 23:6–8, 23–26). These verses double as a caution to the wise to look out for insincerity in others who may not have our best interests in mind.

Even a child is known by his deeds also suggests that our behavior is the most decisive proof test of uprightness and virtue. A child may say, “I’m a well-behaved kid.” But if he disobeys his parents and teachers, starts fights, breaks the law, and constantly seeks out trouble, his actions reveal the true story. As children are known by their conduct, so we should all be distinguished by purity, genuineness, sincerity, and truthfulness in our commitment to God and in our service toward others.

Conduct is the best judge of inner integrity. Our words may reveal our innermost nature (Matthew 12:33–37), but they can be deceiving. Actions and deeds are the better evaluators (James 2:14–26; 1 John 3:18). The wise person will not only listen to what people say but also observe what people do (see Proverbs 20:12).

Jesus taught the principle of knowing people by their actions: “Beware of false prophets who come disguised as harmless sheep but are really vicious wolves. You can identify them by their fruit, that is, by the way they act. Can you pick grapes from thornbushes, or figs from thistles? A good tree produces good fruit, and a bad tree produces bad fruit. A good tree can’t produce bad fruit, and a bad tree can’t produce good fruit. So every tree that does not produce good fruit is chopped down and thrown into the fire. Yes, just as you can identify a tree by its fruit, so you can identify people by their actions” (Matthew 7:15–20, NLT).

Even a child is known by his deeds has an additional implication. The Hebrew noun translated as “child” in Proverbs 20:11 refers to a young person around the age of adolescence. The term indicates one who is still living with and dependent on his parents. The verb rendered “is known” carries the idea of making people recognize what kind of person he is. The Good News Translations expresses the sentiment well: “Even children show what they are by what they do; you can tell if they are honest and good” (Proverbs 20:11, GNB).

God is interested in the condition of our hearts in childhood and not just in adulthood. The formation of a person’s character begins at an early age. Wise parents pay attention to their child’s actions and do their best to “train up a child in the way he should go” so that “even when he is old he will not depart from it” (Proverbs 22:6, ESV).